568 THE NERVOUS SYSTEM. 



morbid action which, distant organs manifest. It has also 

 been called the nervous system of organic life, upon the sup- 

 position, now proved erroneous, that it alone, as a nervous 

 system, influences the organic processes. Both terms are 

 defective; but, since the title sympathetic nerve has the 

 advantage of long and most general custom in its favour, 

 and is not more inaccurate than the other, it will be here 

 emploj^ed. 



The general differences between the fibres of the cere- 

 bro-spinal and sympathetic nerves have been already 

 stated (p. 468) ; and it has been said, that although such 

 general differences exist, and are sufficiently discernible in 

 selected filaments of each system of nerves, yet they are 

 neither so constant, nor of such a kind, as to warrant the 

 supposition, that the different modes of action of the two 

 systems can be referred to the different structures of their 

 fibres. Rather, it is probable, that the laws of conduction 

 by the fibres are in both systems the same, and that the 

 differences manifest in the modes of action of the systems 

 are due to the multiplication and separation of the nervous 

 centres of the sympathetic : ganglia, or nerve-centres, being 

 placed in connection with the fibres of the sympathetic in 

 nearly all parts of their course. 



According to the most general view, the sympathetic 

 S3 r stem may be described as arranged in two principal 

 divisions, each of which consists of ganglia and connecting 

 fibres. The first division may include those ganglia which 

 are seated on and involve the main trunks or branches of 

 cerebral and spinal nerves. This division will include the 

 large Gasserian ganglion on the sensitive trunk of the fifth 

 cerebral nerve (fig. 152), the ganglia on the glosso-pharyn- 

 geal and pneumogastric nerves, and the ganglia on the 

 posterior or sensitive branches of the spinal nerves (fig. 141)- 

 To the second division belong the double chain of prrc- 

 vertebral ganglia (24 to 30, fig. 151) and their branches, 

 extending from the interior and base of the skull to the 



